Previous studies

In November 2003, the Court ordered a study of the mercury in the Penobscot River (Implementing Order) and identified that the purpose of the study was to:

1. Resolve the following issues:

a.

the extent of the existing harm resulting from mercury contamination to the Penobscot River and Bay south of the HoltraChem site at Orrington, Maine (“the site”).

b.

the need for and feasibility of a remediation plan to effectively address the present effects of such existing harm, if any.

c.

the elements of and timetable for the execution of the appropriate remediation plan to address the harm existing as a result of mercury contamination.

2. Answer the following questions:

a.

What physical, chemical and biological processes are presently at work that effect or govern the distribution and fate of mercury and methylmercury in the sediments and plant and animal life of the Penobscot River and Bay system south of the immediate area of the site?

b.

What is the extent to which any mercury in the Penobscot River and Bay system is being methylated and bioconcentrated and biomagnified in aquatic organisms and food webs of the Penobscot River and Bay system?

c.

Is any mercury in the Penobscot River and Bay system having significantly adverse effects on populations of organisms in the lower Penobscot River and Bay system?

d.

Is any mercury in the Penobscot River and Bay system posing an unacceptable risk to human health?

e.

Do the scientific data lead to the conclusion that a mercury remediation program is necessary and feasible to effectively remediate the effects of any such harm caused by mercury contamination in the Penobscot River and Bay system?

f.

If remediation is deemed necessary and feasible, what are the elements of and schedule required for the execution and completion of such a remediation program, addressing the effects of mercury contamination in the Penobscot River and Bay system, and what additional information is needed in order to design the remediation program?

As directed by the Court, a panel of three scientists (the Study Panel) who specialize in mercury and contaminated ecosystems studied the impacts of mercury on the Penobscot River and Estuary.

In January 2008, the Study Panel submitted its findings in the Penobscot River Mercury Study, Phase I of the Study: 2006-2007 (Phase I Report). In this Phase I Report, the Study Panel used four criteria to decide if the environment and and biota of the Penobscot River and Estuary have mercury concentrations at a level that would justify proceeding to a Phase II Study and whether the source of that mercury appears to be the HoltraChem plant site.

The Phase I Report concluded that there was enough scientific evidence to determine that the Penobscot River and Estuary is contaminated with mercury to an extent that poses risks to some wildlife species, and possibly some limited risk for human consumers of fish and shellfish. The Study Panel recommended that the study proceed to a second phase.

In March 2008, the Court adopted the Phase I Report and ordered the Phase II Study to proceed.

In July 2009, the Study Panel submitted an updated Phase I Report (Phase I Report Update), which provided additional data and analysis that confirmed and strengthened the Phase I conclusions.

Phase II Study and Findings

A Phase II Study Plan was originally submitted in March 2008 but was ordered to be revised in April 2008. In May 2008, the Study Panel submitted a Revised Phase II Study Plan (Phase II Study Plan). The Court approved the Revised Phase II Study Plan in July 2008.

In April 2013, the Study Panel submitted its Final Report (Phase II Report) (Executive Summary and Table of Contents, all chapters available in the Information repository). The Phase II Report concluded that inorganic mercury discharged from the HoltraChem plant is present in high concentrations in sediments found in the study area of the Penobscot River and Estuary. It also concluded that mercury is being converted by bacteria into methyl mercury, an organic form of mercury that enters and persists in the bodies of certain animals that ingest it. And that this methyl mercury “biomagnifies” in the food chain, meaning it becomes more concentrated as it passes from prey to predator (see Mercury Background).

The Phase II Report noted that total mercury concentrations are declining in some areas, but at the current rate of decline the Study Panel forecast that it will take approximately 106 to 390 years (depending on the location) for the mercury concentrations to decrease to a level in the main channel that no longer negatively impact plant and animal life. The Phase II Report attributed this slow rate of decline of mercury concentrations to the presence of a large pool of mercury-impacted mobile sediment (estimated at 320,000 tonnes of sediment) that has been trapped in the upper estuary by the natural tendency of estuaries to have bottom waters that flow from the ocean towards the land. This large pool of contaminated sediment is referred to as “the mobile pool”.

Based on the continuing risks, the Study Panel recommended developing a remediation program to reduce mercury contamination in sediments and animals in the Penobscot River and Estuary.